class CkeditorPictureUploader

For images you might use something like this:
Add a white list of extensions which are allowed to be uploaded.

def extension_white_list
  Ckeditor.image_file_types
end

This is a sensible default for uploaders that are meant to be mounted:
Override the directory where uploaded files will be stored.

def store_dir
  "uploads/ckeditor/pictures/#{model.id}"
end